Researchers develop sound way to improve smartphone battery life

Fed up of your smartphone or tablet running out of juice before the end of the day? Why not just make sure the mic is turned on?

It may seem counterintuitive to save power by adding to the things slurping away at your battery, but a group of researchers from Old Dominion University in Virginia have devised a system that does just that. It uses a smartphone or tablet's microphone to detect very high frequency communications to reduce the power consumption of Wi-Fi components.

As Mostafa Uddin, a computer scientist at Old Dominion explained to V3, continuous use of Wi-Fi is one of the chief draws on a smart device's power. Typically, the smartphones and tablets use a power-saving mechanism that wakes the Wi-Fi interface periodically to check it can communicate with a Wi-Fi access point, and check whether any data needs to be pulled from the access point.

Uddin and his supervisor, Tamer Nadeem, realised that this even in this sleepy state, the Wi-Fi interface was proving to be a heavy draw on battery power, so they set about devising a lower-energy alternative.

Instead of using the Wi-Fi interface to check whether any data needed downloading from an access point, they developed an audio signal that can do the same job, a system they dubbed A2PSM.

The A2PSM signal is transmitted at 18KHz, which is more than capable of being picked up by a smartphone's microphone, but too high for the human ear to detect.

“[It was also] distinctive enough to detect in the background noise,” said Uddin - with most of the background noises are below 6kHz.

They showed, using a pair of Nokia N900 handsets, that the signal is also capable of being transmitted and received at a distance of three metres – equivalent to typical distances between smart devices and Wi-Fi access points.

“Theoretically, A2PSM scheme should be able to support up to 30 metres of distance if we could transmit the acoustic signal with enough power,” added Uddin.

What's more, the audio signal saves 25 percent more power than a traditional Wi-Fi wake-up mechanism.

The work will be presented at the HotMobile conference in Jekyll Island, Georgia later this month.